Atlas Of Ferns Of The British Isles

8 LYCOPODIACEAE
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4 .1x c
DIPHASIASTRUM
x ISSLERI
CHANNEL ISLANDS
PLOT TED ON
UTM GRID
Kilometres
Miles
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wv
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100 4457
100
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8
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O
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4.1 x c. Diphasiastrum x issleri (Rouy) Holub
(D.alpinum x complanatum (L.) Holub; Lycopodium
var. deelPiens Syme ex Druce)
Following studies by Lawalrée (Bull. Soc. R. bot. Belg., 9: 109-
120; 1957) records of this taxon appeared in British literature
but confusion and doubt has persisted as to its true identity.
J.Wilce (Beih. Nov. Hedw. 19: 93; 1965) suggests it is a hybrid
derivative of the species mentioned above. Work carried out by
I.Kukkonen (Ann. Bot. Fenn., 4:441-470; 1967) and A.Pacyna
(Fragm. Fl. Geobot., 18: 255-297, 309-341; 1972) supports this
and Pacyna has identified British material as being conspecific
with Polish plants. The shape of the ventral median leaf and
elongated leafy peduncles are diagnostic. Sowerby (Engl. Bot.,
ed 3.t. 1834*; 1886) illustrates plants from v.c. 37, named by
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N1
HX
HW N2
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issleri (Rouy) Lawalrée; Lycopodium alpinum L.
Syme in the legend as Lycopodium alpinum var. decipiens, a
name later validated with a description by Druce (Ann. Scot.
nat. Hist., 1892: 184; 1892). Subsequent botanists have used
this name for a number of atypical D.alpinum gatherings from
Scotland, some of which are most certainly growth forms from
dense vegetation of the latter species. Although of hybrid origin
the spores are only partly abortive and it can spread outside the
range of the parents. However, D.complanatum may yet be
found in Britain in dwarf shrub communities in areas of ancient
woodland.
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